Trigger lock arrangement for power tools



Dec. 5, 1967 A. H. FRANCE. JR 3,356,814

TRIGGER LOCK ARRANGEMENT FOR POWER TOOLS Filed Oct. 24. 1965 V0INVENTOR.

ALF/e50 H. Hen/v05, Jie.

BY M ATTORNEYS United States Patent Ofiice 3,356,814 Patented Dec. 5,1967 3,356,814 TRIGGER LOCK ARRANGEMENT FOR POWER TOOLS Alfred H.France, Jr., Baltimore County, Md., assignor to The Black and DeckerManufacturing Company,

Towson, Md., a corporation of Maryland Filed Oct. 24, 1965, Ser. No.504,697 7 Claims. (Cl. 200-157) ABSTRACT OF THE DISCLOSURE A switch fora portable power tool or appliance which includes an actuatormanipulable to switch OFF and to switch ON positions. The switch has alocking member normally biased outwardly to a non-locking position inwhich an end portion of the locking member projects from the housing.The locking member can be moved inwardly to a locking position after theswitch is turned ON to lock the switch in its ON position. Theimprovement to the switch includes a recess formed in the switchactuator which permits free movement of the locking member to a positionin which its end portion is flush with the housing when the switchactuator is in the OFF position. Thus, damage to the locking member andthe switch is avoided in the event the tool or appliance, while OFF, isdropped or inadvertently struck against an object.

This invention relates to a lock arrangement to maintain a spring biasedtrigger switch of a portable power operated device in an on condition,and particularly to an improved trigger switch lock arrangement whichprevents damage to the trigger, its associated switch, and to the poweroperated device, which could occur as the result of shock or impact atan exposed portion of the lock device.

More particularly, the invention relates to a lock arrangement for thetrigger and switch of a portable electric tool which prevents damagethereto in the event of shock or impact to the locking device such ascan be caused by accidentally dropping or bumping the tool. Portablepower driven tools, especially electric drills, are customarily providedwith a trigger mounted on a handle of the tool to provide for convenientholding and operation of the tool by the user. The normal arrangement isa trigger connected to a switch so that the motor of the tool is turnedon when the trigger is pulled and is immediately turned 01f when thetrigger is released, the trigger and switch being returned to theoriginal released position by a return spring. It is also customary toprovide a manually operable lock to permit the user of the tool to lockthe trigger in the switch on position so the tool remains on after thetrigger is released. In the usual arrangement slight pressure on thetrigger, in its locked condition, disengages the lock, and the triggerthen returns to its switch oif position when released.

As a result of keen competition in the portable power tool field, andbecause of the large number of portable tools manufactured, smallsavings in manufacturing costs are quite significant to the overallprofit of a particular manufacturer. Hence, trigger operated switchesare manufactured from molded plastic materials because of theirrelatively low cost and excellent electrical insulating properties, andare provided as a preassembled unit which is mounted in the tool handle.

A common lock arrangement for triggers of such portable power tools is alock pin that has a knob which projects outwardly from the tool housingand is normally spring biased to a non-locking position in which theknob is exposed. A recess is provided in a movable part of the triggerswitch to receive the pin after the trigger is pulled to the switch onposition. The recess includes a shoulder which faces in a directionopposite to the direction that the movable part of the trigger switchtravels when the trigger is pulled and the lock pin can be depressedinto the recess to engage behind the shoulder to thus prevent thetrigger from moving back to its switch oii position when released. Theshortcoming of the presently used trigger and lock pin arrangements whenthe trigger is in the switch off position, however, is that the knob isexposed and a portion of the trigger switch is then in the path of thelock pin. Hence, damage to the plastic material trigger or switchassociate-d with the trigger frequently occurs when the power tool isaccidentally dropped or bumped, thereby depressing the lock pin withsufiicient force to break the plastic parts of the trigger switch.

The present invention eliminates the problem of breakage or accidentaldamage to the trigger or switch housing by impact or force on the lockpin. This is accomplished in an extremely economical manner atpractically no additional manufacturing cost. The basic concept is toprovide a space or recess to receive the locking pin should itaccidentally be depressed when the trigger switch of the power tool isin its off position. This recess permits the pin to move axially againstthe bias of its return spring without causing any damage to the trigger,its associated switch, or any other portions of the power tool shouldthe tool be dropped so that it lands on the exposed knob portion of thelock pin. It has been found that providing the space or'recess preventsdamage to the trigger and switch, not only when the knob of the pin issubjected to an axial force but also when the knob is struck a glancingblow which normally would tend to break off the sleeve portion of theswitch housing in which the pin is retained for sliding movement.

Hence, by virtue of the simple expedient of this invention, a triggerand switch arrangement for portable power tools is provided which hasessentially the same low cost and convenience of operation of theconventional trigger switch and lock arrangements and which absolutelyprevents damage to the trigger or switch as a result of shock or impacton the trigger locking element such as can be caused by dropping thetool so it lands on the locking element.

The advantageous features discussed above will become apparent withreference to the drawings which form a part of this specification and inwhich FIG. 1 is a front view of a power tool incorporating the damagepreventing lock pin arrangement of this invention, with portions of thetool housing cut away to show the trigger switch;

FIG. 2 is a view in section taken along lines 2-2 of FIG. 1;

FIG. 3 is a partial sectional view taken along lines 33 of FIG. 2;

FIG. 4 is a sectional view taken along lines 44 of FIG. 3;

FIG. 5 is an enlarged partial view in section taken along lines 5-5 ofFIG. 4; and

FIG. 6 is a pictorial view of the trigger assembly removed from theswitch housing.

Referring now to the drawings and particularly to FIGS. 1 and 2, thereis shown a power tool in the form of an electric d-rill 1 having ahousing 2 with a handle portion 3 depending downwardly from the main orbody portion of the housing to provide a conventional pistol grip athandle portion 3 of the power tool. Mounted within handle portion 3 andofiset slightly toward the upper end of the handle portion is a triggerswitch assembly 4 having a trigger assembly 5 and a switch casing 6.Both trigger assembly 5 and switch casing 6 are preferably formed frommolded plastic material having good electrically insulating properties.Casing 6, as shown at FIGS. 3 and 4 has a topwall 7, an integral endwall8 projecting downwardly a short distance and integral with the topwall,and a pair ofsidewalls 9 and 10 which are integral with and projectdownwardly from the opposite side edges of the topw'all for a distanceabout twice the length of endwall 8; Insertable into thespace betweensidewalls 9 and 10 and belowthe plane of edge 11 of endwall8 is apreassembled stationary contact assembly 12. Stationary contact assembly12 includes a contact support member 13 of molded plastic material withgood electrical insulating properties. Contact support member 13 is ofgenerally rectangular outline configuration and is recessed at one sideas at 14 to receive a first pair of stationarycontacts 15 and 16 whichform part of a first switch and is similarly recessed at the other side(not shown) to receive a second pair of stationary contacts which formpart of a second switch (not shown). Each contact is generally L-shapedand has upwardly projecting portions 17 for engagement by a movablecontact.

Wires 18 and 18' of the power cord 20 are connected to stationarycontact 15 of both pairs of contacts. Wires 19 and 19 are connected tothe opposite terminals of the motor of drill 1.

Stationary contact assembly 12 is secured to casing 6 by a rivet 22which passes through aligned openings in the contact support member 13and each of sidewalls 9 and 10 of the casing.

Mounted in casing 6, immediately beneath topwall 7, for sliding movementalong. a path parallel with the topwall, is the trigger assembly 5.Trigger assembly includes a finger engaging portion 23 formed integralwith an elongated, generally rectangular body portion 24 which ismounted for sliding movement along a straight line path in the generallyrectangular space bounded by topwall 7, endwall 8 and portions ofsidewalls 9 and above stationary contact assembly 12. Body 24 isprovided with two downwardly facing recesses 25 offset slightly on eachside of its longitudinal center in which movable contacts 26 aredisposed for sliding movement with the body portion in insulatedrelation with each other. Extending downwardly from the upper wall ofeach of recesses 25 isa compression spring. 27which normally urge themovable contacts 26 in a direction toward both pairs of stationarycontacts and 16.

Above recesses 25, at the end of body 24 opposite from finger engagingportion 23 is a recess 29 which opens toward endwall 8 and is closed atone side to provide a seat 30 for one end of a .helically woundcompression spring 31. The other end of compression spring 31 bearsagainst the inner face of endwall 8.

Seat 30 is at one side of a transverse wall 32 of, the body portion ofthe trigger assembly. At the other side of transverse wall 32 is a notchwhich provides a transverse stop shoulder 33 engageable with a stop rib34 projecting from the inner surface of topwall 7 to prevent separationof trigger assembly 5 from switch casing 6. The action ofcompressionspring 31 normally urges the trigger to the position of FIG. 4.

Between face 35 of transverse wall 32 and the inner wall 36 of thefinger engaging portion 23 of the trigger are a pair of identicalrecesses 37 and. 38 separated by a wall 39 which provides an abutmentsurface in the form of a transverse shoulder 40.

Projecting transversely outwardly from sidewall 10 and molded integraltherewith, adjacent its upper corner at the edge closest to the triggeris a cylindrical sleeve 41 which provides a guide for a trigger switchlock assembly 42. Lock assembly 42 includes a lock pin 43 the knob andpin can be moved from this first, or released position, to .a second ordepressed position (as shown in dotted lines in FIG. 5) against theaction of spring 46.

To turn the drill on, trigger portion 23 is grasped and pulled to movethe trigger assembly to the position of FIG. 4. Whenmoved to thisposition, eachof the mow able contacts 26 moves beyond a central rib 47of con= tact support member 13 to allow the downwardly pro= jectingrounded tips of the movable contact to enga e the contact portions ofboth pairs of stationary contacts 15 and 16. The movablecontacts thusbridge thefixed contacts to complete the series circuit from Wires 18and 18 of the supply line to the motor of drill 1. With the triggerdepressed to its first or switch on position (FIG; 3), knob 45 may bepressed inwardly (FIG. 3) so that head 44 of the lock. pin enters recess37 and engages be hind shoulder 40. The trigger may then be releasedWhereupon the head 44 of the lock pin presents movement of the triggerassembly to its second position of FIG. 4 or 5, in which the switch isoff. The lock assembly is fric vtionally retained in its depressedposition against the action of spring 46. To release the lock pin, it ismerely necessary to depress the trigger slightly whereupon the head 44disengages from shoulder 40 and compression spring 46 snaps lockassembly 42 back to its disengaged position, as shown in solid lines inFIG. 5. V

In this second position of the trigger assembly, with the switch off,recess 38 is aligned with the head of lock pin 43. Hence, when the pinis depressed, head 44 enters recess 38. Observe that guide 41 and knob45 are so dimensioned and located within handle Portion 3 of theelectric drill that the outer surface 51 of sidewall 48 of the handleportion of the drill is substantially flush with the tip 49 of the knobwhen'the knob is depressed.- Thus, the knob may be depressed when thetrigger is in either its first position in which the switch is offwithout danger of engaging any part of the molded plastic material ofthe body portion 24 of trigger assembly 5. By virtue of thisarrangement, careless use of the 'drill such as dropping same when thetrigger switch is in its second or switch off position so that tip 49hits a surface merely causes knob 45 to be forced inwardly to the dottedline position of FIG. 5 against the action of spring 46, but withoutdamage to the trigger switch assembly 4.

In the prior art structures, recess 38 was not provided with the resultthat the full shock of the pin was taken by the body portion of triggerassembly 5. Because trig ger assembly 5 and all portions of switchcasing 6 are made of a molded plastic material, for example, a Bakelitewhich is somewhat brittle, such forces on the locking pin of prior arttrigger-switches frequently resulted in cracking or shattering of thetrigger assembly or portions of the switch casing. In addition, wherethe blow or force occurred at an angle to the axis of knob 45 such asindicated by arrow 50 of, FIG. 5, guide 41 of prior art trigger switchwould be broken oif, thus requiring replacement of the entire switchassembly. However, with knob 45 free to move when the trigger switch isoff as in this invention,- such a glancing blow as shown by thedirection of arrow 50, merely causes the knob to deflect and force thehead of the pin inwardly into recess 38, without damage to the triggerswitch. 7

'Observe withregard to FIGS. 1 and 2 that switch assembly 4 is mountedwithin the handle portion of the power tool and-is'held in place byappropriate ribs of thehollow'handle portion 3 to retain the trigger andswitch in a proper position relative to sidewall 48 of the housing.Hence, the trigger switch can be easily massproduced because of themolded plastic construction and is also easily mounted in the handle ofthe tool with the outer end of knob 45 in its proper relative positionto be substantially flush with the outer surface of the sidewall whenthe knob is depressed.

In view of the foregoing, it is apparent that applicant has provided aunique trigger and switch of the locking type with a safety featurewhich prevents breakage of the switch housing or trigger even though ofsomewhat fragile construction, due to dropping or mishandling of thepower tool to cause excessive forces to be applied to the projectingknob of the lock pin. This safety feature is economically providedmerely by adding a recess in the body portion of the trigger. The recesspositively prevents damage to the fragile parts of the trigger switch inthe event of shock or other forces acting on the exposed part of thelock pin by permitting the lock pin to absorb such forces by movementinto the recess.

Although a preferred embodiment of the invention is shown and described,it is not intended that the inventive features herein set forth belimited to the preferred embodiment described but that these inventivefeatures have utility in other switches of the locking type.

What is claimed is:

1. In an electric tool having a tool housing;

a switch carried by said housing;

a trigger to operate said switch, said trigger being movable to a firstposition in which said switch is on, and a second position in which saidswitch is off; means normally biasing said trigger to said secondposition;

a lock pin having a knob portion and movable to a depressed position inwhich said knob is flush with said tool housing, and

a released position in which said knob is exposed for manual movement tosaid depressed position;

said trigger having a first recess aligned with said lock pin to receivesaid lock pin with said trigger in said first position;

shoulder means facing toward said first recess and arranged to engagesaid lock pin with said lock pin in said depressed position and saidtrigger in said first position;

the improvement comprising a second recess aligned with said lock pinwith said trigger in said second position;

said second recess having a depth, measured along the path of travel ofsaid lock pin, at least as great as the length of the exposed portion ofsaid lock pin to enable said lock pin to enter said recess whendepressed so that the end of the lock pin is flush with the adjacentportion of said housing; whereby damage to said trigger switch isprevented in the event of shock or impact on said pin caused by droppingor bumping said power tool with said trigger in said second position.

2. An improvement in accordance with claim 1 in which said switchincludes a switch housing; and

said trigger, and said locking device are each retained by said switchhousing for movement relative to said switch housing.

3. In a trigger operated switch assembly adapted to be mounted in a tooland having a switch housing of molded plastic material; switch meanscarried by said switch housing; a trigger assembly; first guide means onsaid housing slidably mounting said trigger assembly for movement alonga predetermined path to a first position in which said switch means isin an on condition, and a second position in which said switch means isin an oil condition; means to retain said trigger assembly againstseparation from said switch housing;

means to normally urge said trigger assembly to said second position;

an abutment shoulder on said trigger assembly and movable therewithalong said predetermined path;

a manually operable locking device having an engaging element engageablewith said abutment shoulder and a manipulable knob portion fixedthereto;

a second guide means on said housing for mounting said locking devicefor movement along a predetermined path of travel from a first positionin which said shoulder engaging element is disposed in the path oftravel of said abutment shoulder, and

a second position in which said shoulder engaging element is spaced fromthe path of travel of said shoulder;

said abutment shoulder being located on one side of the path of travelof said locking device when said trigger is in said first position, and

on the other side of the path of travel of said locking device when saidtrigger is in said second position;

said switch housing including means for mounting same in a tool housingin such a manner that said knob portion of said locking element isexposed relative to said tool housing whenever said locking device is insaid first position, and

is completely received in and at least flush with said tool housingwhenever said locking device is in its second position;

the improvement of means to prevent said locking member as well as theswitch itself from being broken in the event the tool, while the triggeris in said second position, is dropped or inadvertently struck againstan object;

said means comprising a recess in said trigger assembly to freelyaccommodate said shoulder engaging member and thus permit movement ofsaid locking member to its second position whenever said triggerassembly is in its second position.

4. A trigger operated switch assembly in accordance with claim 3 inwhich said trigger assembly is of molded plastic material.

5. In an electric tool or appliance having a housing,

an electric switch in the housing, the switch including a manuallymanipulated switch actuator having on and otf positions, and

a resiliently biased locking member retractable into the housingwhenever the switch actuator is in its on position to selectively lockthe switch in the on position, said locking member being resilientlybiased toward an extended or non-locking position and havmg an endportion which normally projects beyond an adjacent surface of thehousing when the locking member is in the extended position;

the improvement of means to prevent said locking member as well as theswitch itself from being broken or damaged in the event the tool, whilein its off position, is dropped or struck inadvertently against anobject,

said means comprising a recess formed in said switch;

said recess communicating with said locking member in the OE position ofthe switch and allowing said locking member to be temporarily retractedtherein;

said end portion of said locking member when said locking member is soretracted, being at least flush with the adjacent surface of thehousing;

whereby said locking member and said switch are protected againstaccidental breakage.

6. The improvement according to claim 5 wherein 7 8 said switch actuatoris movable rectilinearly between its References Cited on and offpositions; and FOREIGN PATENTS said locking member is movablerectilinearly along a path transverse to the rectilinear direction ofmove- 913'389 12/1962 Great Bntam' ment of said switch actuator.

7. The improvement according to claim 5 wherein said recess is formed insaid switch actuator. H. BURKS, Assistant Examiner.

5 ROBERT K. SCHAEFER, Primary Examiner.

1. IN AN ELECTRIC TOOL HAVING A TOOL HOUSING; A SWITCH CARRIED BY SAIDHOUSING; A TRIGGER TO OPERATE SAID SWITCH, SAID TRIGGER BEING MOVABLE TOA FIRST POSITION IN WHICH SAID SWITCH IS ON, AND A SECOND POSITION INWHICH SAID SWITCH IS OFF; MEANS NORMALLY BIASING SAID TRIGGER TO SAIDSECOND POSITION; A LOCK PIN HAVING A KNOB PORTION AND MOVABLE TO ADEPRESSED POSITION IN WHICH SAID KNOB IS FLUSH WITH SAID TOOL HOUSING,AND A RELEASED POSITION IN WHICH SAID KNOB IS EXPOSED FOR MANUALMOVEMENT TO SAID DEPRESSED POSITION; SAID TRIGGER HAVING A FIRST ALIGNEDWITH SAID LOCK PIN TO RECEIVE SAID LOCK PIN WITH SAID TRIGGER IN SAIDFIRST POSITION; SHOULDER MEANS FACING TOWARD SAID FIRST RECESS ANDARRANGED TO ENGAGE SAID LOCK PIN WITH SAID LOCK PIN IN SAID DEPRESSEDPOSITION AND SAID TRIGGER IN SAID FIRST POSITION; THE IMPROVEMENTCOMPRISING A SECOND RECESS ALIGNED WITH SAID LOCK PIN WITH SAID TRIGGERIN SAID SECOND POSITION; SAID SECOND RECESS HAVING A DEPTH, MEASUREDALONG THE PATH OF TRAVEL OF SAID LOCK PIN, AT LEAST AS GREAT AS THELENGTH OF THE EXPOSED PORTION OF SAID LOCK PIN TO ENABLE SAID LOCK PINTO ENTER SAID RECESS WHEN DEPRESSED SO THAT THE END OF THE LOCK PIN ISFLUSH WITH THE ADJACENT PORTION OF SAID HOUSING; WHEREBY DAMAGE OF SAIDTRIGGER SWITCH IS PREVENTED IN THE EVENT OF SHOCK OR IMPACT ON SAID PINCAUSED BY DROPPING OR BUMPING SAID POWER TOOL WITH SAID TRIGGER IN SAIDSECOND POSITION.